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	$159.38	9.122%	$173.9186	$173.92	$173.90	$173.90
Purchase #2	$30.58	4.718%	$32.0228	$32.02	$32.00	$32.00
Purchase #3	$245.75	7.412%	$263.965	$263.97	$263.95	$264.00
Purchase #4	$209.91	6.320%	$223.1763	$223.18	$223.20	$223.20
Purchase #5	$183.42	3.730%	$190.2616	$190.26	$190.25	$190.30
Purchase #6	$171.25	5.183%	$180.1259	$180.13	$180.15	$180.10
Purchase #7	$84.53	5.675%	$89.3271	$89.33	$89.35	$89.30
7 purchase totals =	$1,084.82		$1,152.7973	$1,152.81	$1,152.80	$1,152.80