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	$118.53	10.765%	$131.2898	$131.29	$131.30	$131.30
Purchase #2	$156.69	10.145%	$172.5862	$172.59	$172.60	$172.60
Purchase #3	$79.36	7.362%	$85.2025	$85.20	$85.20	$85.20
Purchase #4	$125.78	7.645%	$135.3959	$135.40	$135.40	$135.40
Purchase #5	$243.78	4.651%	$255.1182	$255.12	$255.10	$255.10
Purchase #6	$178.28	4.102%	$185.593	$185.59	$185.60	$185.60
Purchase #7	$114.91	7.229%	$123.2168	$123.22	$123.20	$123.20
7 purchase totals =	$1,017.33		$1,088.4024	$1,088.41	$1,088.40	$1,088.40