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	$85.54	7.739%	$92.1599	$92.16	$92.15	$92.20
Purchase #2	$143.60	8.126%	$155.2689	$155.27	$155.25	$155.30
Purchase #3	$86.33	4.470%	$90.189	$90.19	$90.20	$90.20
Purchase #4	$233.31	13.216%	$264.1442	$264.14	$264.15	$264.10
Purchase #5	$175.59	4.389%	$183.2966	$183.30	$183.30	$183.30
Purchase #6	$116.62	3.259%	$120.4206	$120.42	$120.40	$120.40
Purchase #7	$196.92	12.524%	$221.5823	$221.58	$221.60	$221.60
7 purchase totals =	$1,037.91		$1,127.0615	$1,127.06	$1,127.05	$1,127.10