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	$140.50	6.858%	$150.1355	$150.14	$150.15	$150.10
Purchase #2	$160.76	6.616%	$171.3959	$171.40	$171.40	$171.40
Purchase #3	$98.31	11.335%	$109.4534	$109.45	$109.45	$109.50
Purchase #4	$226.92	5.859%	$240.2152	$240.22	$240.20	$240.20
Purchase #5	$243.29	6.812%	$259.8629	$259.86	$259.85	$259.90
Purchase #6	$69.89	3.318%	$72.209	$72.21	$72.20	$72.20
Purchase #7	$110.30	6.320%	$117.271	$117.27	$117.25	$117.30
7 purchase totals =	$1,049.97		$1,120.5429	$1,120.55	$1,120.50	$1,120.60