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	$122.42	4.170%	$127.5249	$127.52	$127.50	$127.50
Purchase #2	$70.86	11.151%	$78.7616	$78.76	$78.75	$78.80
Purchase #3	$159.94	13.824%	$182.0501	$182.05	$182.05	$182.10
Purchase #4	$186.87	13.597%	$212.2787	$212.28	$212.30	$212.30
Purchase #5	$104.97	7.293%	$112.6255	$112.63	$112.65	$112.60
Purchase #6	$231.46	5.159%	$243.401	$243.40	$243.40	$243.40
Purchase #7	$190.30	4.121%	$198.1423	$198.14	$198.15	$198.10
7 purchase totals =	$1,066.82		$1,154.7841	$1,154.78	$1,154.80	$1,154.80