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	$190.32	10.761%	$210.8003	$210.80	$210.80	$210.80
Purchase #2	$130.41	12.637%	$146.8899	$146.89	$146.90	$146.90
Purchase #3	$143.56	6.846%	$153.3881	$153.39	$153.40	$153.40
Purchase #4	$154.56	5.179%	$162.5647	$162.56	$162.55	$162.60
Purchase #5	$175.50	4.424%	$183.2641	$183.26	$183.25	$183.30
Purchase #6	$80.82	12.808%	$91.1714	$91.17	$91.15	$91.20
Purchase #7	$75.56	3.612%	$78.2892	$78.29	$78.30	$78.30
7 purchase totals =	$950.73		$1,026.3677	$1,026.36	$1,026.35	$1,026.50