Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$220.57	3.397%	$228.0628	$228.06	$228.05	$228.10
Purchase #2	$123.56	3.117%	$127.4114	$127.41	$127.40	$127.40
Purchase #3	$249.90	12.772%	$281.8172	$281.82	$281.80	$281.80
Purchase #4	$176.87	10.413%	$195.2875	$195.29	$195.30	$195.30
Purchase #5	$99.41	12.125%	$111.4635	$111.46	$111.45	$111.50
Purchase #6	$116.62	3.165%	$120.311	$120.31	$120.30	$120.30
Purchase #7	$165.37	3.572%	$171.277	$171.28	$171.30	$171.30
7 purchase totals =	$1,152.30		$1,235.6304	$1,235.63	$1,235.60	$1,235.70