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	$86.31	7.126%	$92.4605	$92.46	$92.45	$92.50
Purchase #2	$53.95	7.270%	$57.8722	$57.87	$57.85	$57.90
Purchase #3	$236.49	3.696%	$245.2307	$245.23	$245.25	$245.20
Purchase #4	$238.89	12.521%	$268.8014	$268.80	$268.80	$268.80
Purchase #5	$249.26	7.140%	$267.0572	$267.06	$267.05	$267.10
Purchase #6	$94.30	6.328%	$100.2673	$100.27	$100.25	$100.30
Purchase #7	$94.88	4.661%	$99.3024	$99.30	$99.30	$99.30
7 purchase totals =	$1,054.08		$1,130.9917	$1,130.99	$1,130.95	$1,131.10