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	$165.54	7.852%	$178.5382	$178.54	$178.55	$178.50
Purchase #2	$171.56	11.743%	$191.7063	$191.71	$191.70	$191.70
Purchase #3	$93.27	8.611%	$101.3015	$101.30	$101.30	$101.30
Purchase #4	$14.54	7.592%	$15.6439	$15.64	$15.65	$15.60
Purchase #5	$145.88	4.521%	$152.4752	$152.48	$152.50	$152.50
Purchase #6	$168.71	3.793%	$175.1092	$175.11	$175.10	$175.10
Purchase #7	$240.53	11.645%	$268.5397	$268.54	$268.55	$268.50
7 purchase totals =	$1,000.03		$1,083.3140	$1,083.32	$1,083.35	$1,083.20