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	$170.41	9.233%	$186.144	$186.14	$186.15	$186.10
Purchase #2	$184.88	8.431%	$200.4672	$200.47	$200.45	$200.50
Purchase #3	$179.44	8.293%	$194.321	$194.32	$194.30	$194.30
Purchase #4	$22.61	9.115%	$24.6709	$24.67	$24.65	$24.70
Purchase #5	$93.54	7.801%	$100.8371	$100.84	$100.85	$100.80
Purchase #6	$48.46	9.842%	$53.2294	$53.23	$53.25	$53.20
Purchase #7	$229.36	11.350%	$255.3924	$255.39	$255.40	$255.40
7 purchase totals =	$928.70		$1,015.0620	$1,015.06	$1,015.05	$1,015.00