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	$81.56	11.736%	$91.1319	$91.13	$91.15	$91.10
Purchase #2	$20.26	5.250%	$21.3237	$21.32	$21.30	$21.30
Purchase #3	$209.89	12.146%	$235.3832	$235.38	$235.40	$235.40
Purchase #4	$238.28	13.122%	$269.5471	$269.55	$269.55	$269.50
Purchase #5	$101.74	9.408%	$111.3117	$111.31	$111.30	$111.30
Purchase #6	$241.92	5.194%	$254.4853	$254.49	$254.50	$254.50
Purchase #7	$142.93	13.829%	$162.6958	$162.70	$162.70	$162.70
7 purchase totals =	$1,036.58		$1,145.8787	$1,145.88	$1,145.90	$1,145.80